Research question

What is bioavailability?

Bioavailability is the fraction of an administered dose that reaches systemic circulation in unchanged form. Intravenous administration is the reference 100% bioavailability standard; other routes (subcutaneous, oral, intranasal) have variable bioavailability depending on absorption and first-pass metabolism.

What the research literature says

Bioavailability quantifies how much of an administered dose actually enters systemic circulation in pharmacologically-active form. Intravenous administration has 100% bioavailability by definition — the drug enters the bloodstream directly. Other administration routes have lower bioavailability due to incomplete absorption (subcutaneous, oral) and/or first-pass metabolism in the liver (oral compounds passing through the portal circulation).

For peptide research compounds specifically, subcutaneous administration typically produces high bioavailability (~70-90% for peptides without significant subcutaneous degradation) with delayed absorption profile relative to intravenous. Oral administration of intact peptides typically produces very low bioavailability due to gastric-acid and intestinal-protease degradation; this is why most catalog peptides are supplied for subcutaneous administration rather than oral.

The Johansen ipamorelin pharmacokinetic work characterised oral, nasal, and parenteral bioavailability across administration routes (PMID 9879640). Bioavailability is calculated as the ratio of AUC values between the test administration route and intravenous reference administration at matched doses.

Why this matters in research context

Bioavailability matters in peptide-research contexts when comparing administration routes or interpreting dose-response data across routes. Researchers extrapolating from oral-administration literature to subcutaneous protocols (or vice versa) should account for the substantial bioavailability differences — a 1 mg subcutaneous dose may produce dramatically different plasma exposure than a 1 mg oral dose for the same compound.

Related compounds

Reconstitution guide — subcutaneous administration framework

References

Johansen PB et al. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica 1998;28(11):1083-1095. [PMID 9879640]

Research-questions pages describe research-context use of peptide-research terminology. They do not constitute medical, veterinary, or clinical advice. Every compound in the Ronin catalog is sold strictly for laboratory and research use only.